Dynamic ir emission control for fast recognition of eye tracking system

ABSTRACT

A picture generation unit emits a light field. A mirror reflects the light field toward a windshield of a motor vehicle such that the light field is reflected off of the windshield and is visible to the driver as a virtual image. An infrared emitter transmits infrared energy through the mirror such that the infrared energy is substantially co-axial with the light field, and such that the infrared energy is reflected off of the windshield toward the human driver. An infrared camera captures infrared images based on the transmitted infrared energy reflected off of the human driver and received by the infrared camera. Eye tracking is performed based on the captured infrared images. The infrared energy is transmitted at a higher power level at a beginning of the eye tracking than after the beginning of the eye tracking.

CROSS-REFERENCED TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/682,879, filed Feb. 28, 2022, which claims benefit of U.S.Provisional Application No. 63/158,308, filed on Mar. 8, 2021, thedisclosures of which are hereby incorporated by reference in theirentireties for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an eye tracking system, and, moreparticularly, to an eye tracking system in a motor vehicle.

2. Description of the Related Art

A head up display emits light that reflects from the front windshield tobe seen by the driver. The light appears to come from a virtual image infront of the driver and in front of the windshield. This type of head updisplay is currently commercially available.

Conventional head up displays create the virtual image by first using adisplay or picture generation unit to create an image. Next, the lightfrom the image is reflected from one or more mirrors. Next, the lightfrom the mirrors is directed up to the windshield and is then reflectedfrom the windshield towards the driver. The mirrors are designed andpositioned relative to the display so that the light seen by the driver,which is reflected from the windshield, appears to come from a virtualimage that is outside of the vehicle. The mirrors and display aretypically contained in a package that occupies a volume beneath the topsurface of the dashboard.

There are many eye tracking systems used in motor vehicles, but none ofthem are packaged in a HUD.

SUMMARY OF THE INVENTION

The invention may include an eye tracking system (ETS) embedded in ahead up display (HUD). Using infrared (IR) wavelengths in an eyetracking system (ETS) has the advantage of the ETS hardware beinginvisible to the driver (e.g., hidden in the head up display (HUD)).Another advantage is that the ETS module faces the driver from asubstantially straight angle via reflection from the windshield, whereinvisible image optical pathways are used for more than one purpose, suchas HUD and eye tracking. An IR-based ETS needs good illumination of thedriver's face and takes time to have the face recognized and the eyeposition tracked. The initial pick-up of an eye position is notinstantaneous and takes many seconds or even longer.

The illumination level is important to the operation of an ETS. Use ofIR wavelengths with an IR illuminator enables an ETS to work in bothdaytime and nighttime. The IR illumination strength level may affectwhether or not a face can be tracked (e.g., the illumination level maybe too low for face tracking to be performed) and how quick the facegets tracked. In particular, if the illumination level is too low andthus the driver's face looks very dark, then there is a greater chancethat the eyes cannot be tracked.

The invention comprises, in one form thereof, a head up display and eyetracking arrangement for a motor vehicle, including a picture generationunit emitting a light field. A mirror is positioned to reflect the lightfield toward a windshield of the motor vehicle such that the light fieldis reflected off of the windshield toward a human driver of the motorvehicle and is visible to the driver as a virtual image. An infraredemitter transmits infrared energy through the mirror such that thetransmitted infrared energy is substantially co-axial with the lightfield after the light field has been reflected by the mirror, and suchthat the infrared energy is reflected off of the windshield toward thehuman driver. An infrared camera captures infrared images based on thetransmitted infrared energy reflected off of the human driver, reflecteda second time off of the windshield, and received by the infraredcamera. An electronic processor performs eye tracking based on thecaptured infrared images, and causes the infrared energy to betransmitted at an initial power level at a beginning of the eye trackingand at a later power level after the beginning of the eye tracking. Theinitial power level is greater than the later power level.

The invention comprises, in another form thereof, a display and eyetracking method for a motor vehicle, including emitting a light field. Amirror is positioned to reflect the light field toward a windshield ofthe motor vehicle such that the light field is reflected off of thewindshield toward a human driver of the motor vehicle and is visible tothe driver as a virtual image. Infrared energy is transmitted throughthe mirror such that the transmitted infrared energy is substantiallyco-axial with the light field after the light field has been reflectedby the mirror, and such that the infrared energy is reflected off of thewindshield toward the human driver. The transmitted infrared energy isreceived after the transmitted infrared energy has been reflected off ofthe human driver and reflected a second time off of the windshield. Eyetracking is performed based on the received infrared energy. Theinfrared energy is transmitted at an initial power level during abeginning stage of the eye tracking and at a later power levelimmediately after the beginning stage of the eye tracking. The initialpower level is greater than the later power level.

The invention comprises, in yet another form thereof, a head up displayand eye tracking arrangement for a motor vehicle, including a picturegeneration unit emitting a light field. A mirror is positioned toreflect the light field toward a windshield of the motor vehicle suchthat the light field is reflected off of the windshield toward a humandriver of the motor vehicle and is visible to the driver as a virtualimage. At least one infrared emitter is positioned to emit infraredenergy through the mirror such that the emitted infrared energy issubstantially co-axial with the light field after the light field hasbeen reflected by the mirror, and such that the infrared energy isreflected off of the windshield toward the human driver. An infraredcamera is positioned to capture infrared images based on the emittedinfrared energy reflected off of the human driver, reflected a secondtime off of the windshield, and received by the infrared camera. Anelectronic processor is communicatively coupled to the at least oneinfrared emitter and to the infrared camera. The electronic processorperforms eye tracking based on the captured infrared images. Theinfrared energy is caused to be emitted at an initial brightness levelduring a beginning stage of the eye tracking and at a later brightnesslevel immediately after the beginning stage of the eye tracking. Theinitial brightness level is greater than the later brightness level.

An advantage of the invention is that it uses dynamic control of ETS IRemission to improve ETS pick-up and tracking performance.

Another advantage of the invention is that it enables the driver's face,which is an area that needs to be seen by the eye-tracking camera, to beilluminated more brightly at the beginning of eye tracking to hasten thefirst pick up or recognition of the eyes that are to be tracked.

Yet another advantage of the invention is that it solves in part theproblem that the driver's face may appear dark (or not sufficientlybright) in some existing ETS.

A further advantage of the invention is that it provides enhancedperformance of an ETS without changing the illuminator component orcausing significant thermal effects.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a schematic diagram of one embodiment of a head up display andeye tracking arrangement of the present invention.

FIG. 2 is a plot of infrared emission strength versus time in oneembodiment of an eye tracking system of the present invention.

FIG. 3 is a flow chart of one embodiment of a display and eye trackingmethod of the present invention for a motor vehicle.

DETAILED DESCRIPTION

The embodiments hereinafter disclosed are not intended to be exhaustiveor limit the invention to the precise forms disclosed in the followingdescription. Rather the embodiments are chosen and described so thatothers skilled in the art may utilize its teachings.

FIG. 1 illustrates one embodiment of a head up display (HUD) and eyetracking arrangement 10 of the present invention, including an eyetracking system (ETS) HUD (windshield type) 100 having an IR part (e.g.,an IR energy transmitter/receiver and camera) 102, a picture generationunit (PGU) 104, a fold mirror 106, a freeform (cold) mirror 108, and anelectronic processor or controller 110 that controls the power withwhich IR energy is transmitted by IR part 102 as a function of time.Processor 110 may also analyze the images captured by the IR camera inIR part 102 to detect the position of the head or eyes of a human driver114 in the images. Head up display (HUD) and eye tracking arrangement 10further includes windshield 112.

FIG. 1 shows a schematic of a traditional ETS HUD (windshield type) 100,with the ETS camera of IR part 102 on the optical axis and multiple IRilluminators of IR part 102 disposed around the camera. The emissionfrom different IR illuminators on the same IR part 102, especially theaxial ray, joins the visible axial light ray from picture generationunit (PGU) 104 and fold mirror 106 at the freeform (cold) mirror 108.The visible light is reflected by different areas on mirror 108 and,along with the IR energy that transmits through mirror 108, issubsequently reflected by windshield 112 toward human driver 114. Thevisible light and IR energy eventually reach the driver 114, and thusthe driver can see a virtual image 116 that appears to be outside ofwindshield 112 ahead of the vehicle. The axial rays 120, 122 that startfrom the center of eye box 123 reach the center of the IR camera of IRpart 102. The rays 124 and 126 represent some edge rays or outermostrays from the driver's face that can be seen by the IR camera of IR part102.

When the environment is dark (e.g., during a storm or at nighttime), hasartificial lighting but the IR spectrum is insufficient (e.g., indoorsor in a tunnel), or in any other cases where more IR illumination wouldbe beneficial, an increase of IR illumination from the ETS may bedesirable to supply a greater illumination brightness level on thedriver's face. Such an increase in the illumination brightness level onthe driver's face can be achieved by providing a greater number of IRilluminators or by driving the existing IR illuminators at a higherpower level. The present invention may use dynamic IR emission controlthat delivers a stronger-than-normal light level during the initialpick-up stage of ETS and then adjusts to a normal light level afterwardsto maintain good tracking. In a pulsed or emission scheme, the averageillumination brightness level may be increased by having a longer pulsetime duration or width.

In one embodiment, for both continuous wave (cw) and a pulsed emissionscheme, overshooting the IR emission as soon as the ETS is switched orflashed on may provide a higher-than-normal illumination brightnesslevel at the beginning. FIG. 2 illustrates one example of such dynamicIR emission control. The IR emission strength or brightness levelovershoots and is higher immediately after the ETS is turned on, andthen stabilizes at the normal steady-state brightness level.

In another embodiment for a pulsed emission scheme, the duty cycle ofthe LEDs is set to a higher-than-normal level as soon as the ETS isswitched or flashed on. For example, during the first few seconds afterthe ETS is switched on, the LEDs may be provided with higher and dynamicduty cycle control until the first face pick-up in the ETS.

In yet another embodiment, the driving current and/or the voltage of theLEDs is automatically set higher (via an electric circuit designed toenable) to achieve more emission power at the beginning of eye tracking.

In a further embodiment, both duty cycle and emission power are sethigher at the beginning of eye tracking.

In still another embodiment, a strong spike modeled as a delta pulse orunit impulse (having a time duration approximately between onemicrosecond and one second) of emission is enabled at the beginning ofeye tracking. This ultra-short and ultra-strong emission pulse may helpto quickly catch the first face pick-up.

In a still further embodiment, a dynamic beam shaping lens withbeam-angle tenability may be used to achieve a higher brightness levelof the face by adjusting to a narrow beam angle at the beginning of eyetracking to concentrate more light on the face.

There could be a situation where the environmental lighting (e.g.sunlight) is already too strong, and additional IR emission would notenable any better performance. In such cases, IR illuminators may not beturned on until the environmental lighting becomes weaker.

FIG. 3 is a flow chart of one embodiment of a display and eye trackingmethod 300 of the present invention for a motor vehicle. In a first step302, a light field is emitted. For example, picture generation unit(PGU) 104 may emit a light field.

Next, in step 304, a mirror is positioned to reflect the light fieldtoward a windshield of the motor vehicle such that the light field isreflected off of the windshield toward a human driver of the motorvehicle and is visible to the driver as a virtual image. For example,mirror 108 is positioned to reflect the light field toward a windshield112 of the motor vehicle such that the light field is reflected off ofwindshield 112 toward a human driver 114 of the motor vehicle and isvisible to driver 114 as a virtual image 116.

In a next step 306, infrared energy is transmitted through the mirrorsuch that the transmitted infrared energy is substantially co-axial withthe light field after the light field has been reflected by the mirror,and such that the infrared energy is reflected off of the windshieldtoward the human driver. For example, infrared energy from an IR energytransmitter of IR part 102 is transmitted through mirror 108 such thatthe transmitted infrared energy is substantially co-axial with the lightfield after the light field has been reflected by mirror 108, and suchthat the infrared energy is reflected off of windshield 112 toward humandriver 114.

In step 308, the transmitted infrared energy is received after thetransmitted infrared energy has been reflected off of the human driverand reflected a second time off of the windshield. For example, thetransmitted infrared energy is received by the IR energy receiver of IRpart 102 after the transmitted infrared energy has been reflected off ofhuman driver 114 and reflected a second time off of windshield 112.

In a final step 310, eye tracking is performed based on the receivedinfrared energy, wherein the infrared energy is transmitted at aninitial power level during a beginning stage of the eye tracking and ata later power level immediately after the beginning stage of the eyetracking. The initial power level is greater than the later power level.For example, eye tracking is performed by electronic processor orcontroller 110 based on the received infrared energy, wherein theinfrared energy is transmitted at a relatively high initial power levelduring a beginning stage of the eye tracking and at a relatively lowlater power level immediately after the beginning stage of the eyetracking, as shown in FIG. 2 .

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A head up display and eye tracking arrangementfor a motor vehicle, the arrangement comprising: a picture generationunit configured to emit a light field; a mirror positioned to reflectthe light field toward a windshield of the motor vehicle such that thelight field is reflected off of the windshield toward a human driver ofthe motor vehicle and is visible to the driver as a virtual image; atleast one infrared emitter positioned to transmit infrared energythrough the mirror such that the transmitted infrared energy issubstantially co-axial with the light field after the light field hasbeen reflected by the mirror, and such that the infrared energy isreflected off of the windshield toward the human driver; an infraredcamera positioned to capture infrared images based on the transmittedinfrared energy reflected off of the human driver, reflected a secondtime off of the windshield, and received by the infrared camera; and anelectronic processor communicatively coupled to the at least oneinfrared emitter and to the infrared camera, the electronic processorbeing configured to: perform eye tracking based on the captured infraredimages; and cause the infrared energy to be transmitted at an initialpower level during a beginning stage of the eye tracking and at a laterpower level immediately after the beginning stage of the eye tracking,the initial power level being greater than the later power level.
 2. Thearrangement of claim 1 wherein the mirror comprises a freeform mirror,the arrangement further comprising a fold mirror, the fold mirror beingpositioned to reflect the light field toward the freeform mirror.
 3. Thearrangement of claim 1 wherein the initial power level is at least 80percent greater than the later power level.
 4. The arrangement of claim1 wherein the later power level comprises a steady-state power level. 5.The arrangement of claim 1 wherein the electronic processor isconfigured to cause the infrared energy to be transmitted at an initialduty cycle during the beginning stage of the eye tracking and at a laterduty cycle immediately after the beginning stage of the eye tracking,the initial duty cycle being greater than the later power duty cycle. 6.The arrangement system of claim 1 wherein the at least one infraredemitter comprises a first infrared emitter and a second infraredemitter, the electronic processor being configured to cause the secondinfrared emitter to be on during the beginning stage of the eye trackingand off immediately after the beginning stage of the eye tracking, andremain off for a time duration at least half as long as a time durationof the beginning stage of the eye tracking.
 7. The arrangement of claim1 wherein the electronic processor is configured to cause the infraredenergy to be transmitted at the later power level for a time duration atleast half as long as a time duration of the beginning stage of the eyetracking.
 8. A display and eye tracking method for a motor vehicle, themethod comprising: emitting a light field; positioning a mirror toreflect the light field toward a windshield of the motor vehicle suchthat the light field is reflected off of the windshield toward a humandriver of the motor vehicle and is visible to the driver as a virtualimage; transmitting infrared energy through the mirror such that thetransmitted infrared energy is substantially co-axial with the lightfield after the light field has been reflected by the mirror, and suchthat the infrared energy is reflected off of the windshield toward thehuman driver; receiving the transmitted infrared energy after thetransmitted infrared energy has been reflected off of the human driverand reflected a second time off of the windshield; and performing eyetracking based on the received infrared energy, wherein the infraredenergy is transmitted at an initial power level during a beginning stageof the eye tracking and at a later power level immediately after thebeginning stage of the eye tracking, the initial power level beinggreater than the later power level.
 9. The method of claim 8 furthercomprising producing infrared images based on the received infraredenergy, wherein the eye tracking is performed based on the infraredimages.
 10. The method of claim 8 wherein the mirror comprises afreeform mirror, the method further comprising positioning a fold mirrorto reflect the light field toward the freeform mirror.
 11. The method ofclaim 8 wherein the initial power level is at least 80 percent greaterthan the later power level.
 12. The method of claim 8 wherein the laterpower level comprises a steady-state power level.
 13. The method ofclaim 8 wherein the infrared energy is transmitted at an initial dutycycle during the beginning stage of the eye tracking and at a later dutycycle immediately after the beginning stage of the eye tracking, theinitial duty cycle being greater than the later power duty cycle. 14.The method of claim 8 wherein the infrared energy is transmitted by botha first infrared emitter and a second infrared emitter during thebeginning stage of the eye tracking, and the second infrared emitter isoff immediately after the beginning stage of the eye tracking.
 15. Themethod of claim 8 wherein the infrared energy is transmitted at thelater power level for a time duration at least 75 percent of the timeduration of the beginning stage of the eye tracking.
 16. A head updisplay and eye tracking arrangement for a motor vehicle, thearrangement comprising: a picture generation unit configured to emit alight field; a mirror positioned to reflect the light field toward awindshield of the motor vehicle such that the light field is reflectedoff of the windshield toward a human driver of the motor vehicle and isvisible to the driver as a virtual image; at least one infrared emitterpositioned to emit infrared energy through the mirror such that theemitted infrared energy is substantially co-axial with the light fieldafter the light field has been reflected by the mirror, and such thatthe infrared energy is reflected off of the windshield toward the humandriver; an infrared camera positioned to capture infrared images basedon the emitted infrared energy reflected off of the human driver,reflected a second time off of the windshield, and received by theinfrared camera; and an electronic processor communicatively coupled tothe at least one infrared emitter and to the infrared camera, theelectronic processor being configured to: perform eye tracking based onthe captured infrared images; and cause the infrared energy to beemitted at an initial brightness level during a beginning stage of theeye tracking and at a later brightness level immediately after thebeginning stage of the eye tracking, the initial brightness level beinggreater than the later brightness level.
 17. The arrangement of claim 16wherein the initial power level is at least 80 percent greater than thelater power level.
 18. The arrangement of claim 16 wherein theelectronic processor is configured to cause the infrared energy to beemitted at an initial duty cycle during the beginning stage of the eyetracking and at a later duty cycle immediately after the beginning stageof the eye tracking, the initial duty cycle being greater than the laterpower duty cycle.
 19. The arrangement system of claim 16 wherein theelectronic processor is configured to cause the at least one infraredemitter to be on during the beginning stage of the eye tracking and offimmediately after the beginning stage of the eye tracking, and remainoff for a time duration greater than a time duration of the beginningstage of the eye tracking.
 20. The arrangement of claim 16 wherein theelectronic processor is configured to cause the infrared energy to beemitted at the later brightness level for a time duration at least 25percent of a time duration of the beginning stage of the eye tracking.